How to switch between different java versions in ubuntu?

Assume you have java-7-oracle and java-8-oracle installed in your machine and now you need to switch between these 2 versions of java.

In order to check which version you are currently using in the machine, execute the command below in the terminal.

java -version

You will see an output similar to the following.

Now to switch to java-8-oracle, execute the below command in the terminal.

sudo update-alternatives --config java

You will see an output like below. It lists down all the java installations in your machine.

Enter the selection number in the prompt. In this case, it will be 2 as we need to switch to java-8-oracle. 

Now you should export the JAVA_HOME variable with the new version by adding the following to the .bashrc file. You can take the path from the prompt above.

export JAVA_HOME=/usr/lib/jvm/java-8-oracle

Then you can open a new terminal and type the following command to check whether the java version has changed.

java -version

Cheers!